At present, a Wireless Local Access Network (WLAN) develops quickly in the wireless network field, with growing demands on WLAN coverage and higher demand WLAN throughput. Institute of Electrical and Electronic Engineers (IEEE802.11) successively defines a series of most common WLAN technical standards (such as 802.11a, 802.11b, 802.11g and the like); subsequently, other task groups appear one after another to be committed to developing standards involved in improvement of existing 802.11 technology, for example, task group 802.11n proposes a requirement of High Throughput (HT), which supports a data rate up to 600 Mbps; task group 802.11ac further proposes a concept of Very High Throughput (VHT), which increases the data rate to 1 Gbps by introducing a greater channel bandwidth.
According to the IEEE802.11, one Access Point (AP) and multiple Stations (STAs) associated with this AP form a Basic Service Set (BSS).
The IEEE802.11 defines two operation modes: a Distributed Coordination Function (DCF) and a Point Coordination Function (PCF), and also defines improvements aiming at the two operation modes: an Enhanced Distributed Channel Access (EDCA) function and a Hybrid Coordination Function Controlled Channel Access (HCCA) function. The DCF is the most basic operation mode, which enables multiple stations to share one radio channel by adopting a Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) mechanism. The EDCA function is an enhanced operation mode, which enables multiple access categories of different priorities to share one radio channel by adopting the CSMA/CA mechanism and appoints a Transmission Opportunity (TXOP), that is, transmission duration (TXOP Duration). Each priority queue with QoS requirements has a transmission time limit (TXOP limit) parameter respectively. The TXOP limit indicates the maximum transmission duration corresponding to the TXOP obtained by the priority queue. A Transmission Network Allocation Vector counter (TXNAV Timer) is set while the transmission time is appointed, and the initial value is set to TXOP Duration. The TXOP Duration is set according to the transmission duration, which must be less than or equal to the TXOP limit. The initial time set by the TXOP limit and the TXNAV Timer is called a transmission time threshold.
In the related art, a new frame switch sequence is defined for measurement of channel information; specifically, a transmitting station transmits a Null Data Packet Announcement (NDPA) frame for measurement of channel, and transmits a Null Data Packet (NDP) frame after a Short Interframe Space (SIFS) upon the end of transmission of NDPA frame; then, the first station indicated by the default NDPA frame replies channel feedback information (Sounding Feedback) after an SIFS upon the complete of receiving of the NDPA frame and the NDP frame. If there are multiple receiving stations, except the first station which feeds back information by default, other receiving stations wait a Beamforming Report Poll from the transmitting station to transmit channel feedback information, as shown in FIG. 1.
The measurement of channel information performed by the above stations is very important for both parties of communication. The purpose of this process is to ensure both parties of communication to efficiently perform subsequent data service communications. According to the related art, generally, when a transmitter and a receiver are performing communications, the transmitter would not transmit a frame unless it estimates that the sum of the duration needed to transmit the frame, the duration needed to transmit a response frame by the receiver and the necessary interframe interval does not exceed the transmission time threshold. However, for the measurement process of channel information, a data volume and a data transmission rate of the channel feedback information fed back by the receiving station would differ depending on different channel conditions; in this way, the transmitter cannot estimate the data volume and rate of the channel feedback information fed back by the receiving station, and thus cannot learn whether the time for feeding backing the channel feedback information by the receiver would exceed the transmission time threshold or not. If at this time the transmitter does not transmit a radio frame to request the receiver to feed back channel feedback information, the transmitter cannot obtain the channel feedback information timely.